1. Field
The present specification generally relates to optical fibers used as fiber lasing media and, more specifically, to photodarkening resistant optical fibers and methods for making the same.
2. Technical Background
Optical fibers doped with active rare-earth dopants, such as ytterbium and the like, are commonly employed in fiber laser systems. Fiber laser systems employing such fibers are commonly utilized in applications where a laser is needed with both high brightness and high output power. However, one drawback of fiber laser systems is the photo-darkening of the active gain medium in high power fiber lasers.
More specifically, photodarkening occurs in ytterbium-doped optical fibers used as the active gain media in fiber laser systems, particularly after the pump laser of the fiber laser system has been operated at high pump powers which exceed a certain power-intensity threshold. Photodarkening is manifested as a measurable loss in the optical output power of the active gain media during lasing. With continued operation of the fiber laser system, photodarkening results in the progressive loss of optical output power which damages the optical fiber and, in extreme cases, causes the lasing or gain action of the fiber to terminate As such, photodarkening impacts both the reliability and safety of devices which incorporate fiber laser systems utilizing rare-earth doped optical fibers, such as ytterbium-doped optical fibers.
Accordingly, a need exists for alternative optical fibers for use in fiber lasing systems and methods for producing the same.